Various applications require a sensor to detect a physical quantity, such as a position, e.g. a linear or angular position of an object. It is known in the art to measure a magnetic field property of a magnetic field, e.g. using a magnetic sensor, in combination with a magnetic field generating and/or influencing element, e.g. a magnetized object or an object that alters a magnetic field. The magnetic sensor and this element may be typically arranged such as to be movable, e.g. rotatable and/or translatable, with respect to each other. Thus, the magnetic sensor may measure a property of the magnetic field emanating from or influenced by the object, in which this property in indicative for the relative position and/or orientation of the element with respect to the sensor. For example, a linear position sensor may determine the position of an object on a linear path relative to the sensor, and an angular sensor may determine an angular orientation of an object relative to the sensor.
The property of the magnetic field being measured may be the strength of the magnetic field, which can be directly measured, for example by Hall sensor elements. Another property may be the magnetic flux, which may be measured indirectly, e.g. by an induced current. For example, an inductive sensor element may be used, such as a coil. It is also known in the art to measure the strength of one or more magnetic field components, e.g. the projection(s) of the magnetic field vector in a particular direction(s).
Furthermore, more than one property of the magnetic field may be measured, and/or such property or properties may be measured in multiple sensing locations. The plurality of measurements may then be combined and/or processed to determine the position information of interest.
For example, it is known in the art to determine an angle of a shaft using a magnetic sensor. In such prior art devices, a magnet may be mechanically linked to a gear wheel, and a magnetic sensor is used to determine the angular position of the magnet. Different magnetic sensors may detect the magnetic fields of corresponding magnets linked to the shaft via corresponding gear wheels, in which each gear wheel has a different gear transmission ratio with respect to a hub gear wheel mechanically connected to the input shaft. Thus, such magnetic sensors may use the nonius principle to achieve an accurate angle determination.
In another example, US 2015/226581 discloses an arrangement for measuring an angular position of a rotor with respect to a stator. This arrangement comprises a multi-pole magnet mounted on the rotor, a sensor mounted on the stator and a plurality of sensor elements organized in two groups or four groups for measuring a magnetic field component. A method for calculating the angular position based on the signals of the elements of each group is disclosed. Thus, a magnetic sensor can be provided that measures a magnetic field of a multipole magnet, while being substantially insensitive to a dipole field.
In a different example, US 2005/0151535 discloses a magnetic linear position sensor that comprises a first yoke and a first and second magnet on the first yoke. Surfaces of the first magnet and the second magnet, inclined in opposite directions, respectively form a magnetic north pole and a magnetic south pole. A second yoke is placed at a position opposing the first and second magnet, separated by an air gap. A magnetoelectric transducer is placed in the air gap to sense the linear position.